The present study evaluated the effects of Quillaja saponin (QS) supplementation on growth efficiency, nutritional digestibility, gas emissions, and faecal score in growing pigs. In a 42-day experiment, 80 growing pigs [(Yorkshire × Landrace) × Duroc] were randomly assigned (29.17 ± 0.23 kg initial average body weight) to 2 different trial groups. Each group had 8 replicates, consisting of 3 male and 2 female pigs in each pen. The nutritional treatments included a control group (CON) receiving a basal diet and a treatment group (TRT1) receiving a basal diet supplemented with 0.01% QS. The results of this study indicated that pigs consuming the QS-supplemented diet exhibited significantly higher (P < 0.05) body weight on day 42 compared to the CON group. Furthermore, dietary QS led to higher (P < 0.05) average daily gain and showed a tendency to reduce (P < 0.10) the feed conversion ratio throughout the study period, as compared to the CON diet. Growing pigs that consumed the QS-supplemented diet also showed higher (P < 0.05) nutrient utilisation of dry matter and nitrogen compared to the CON group. At day 42, QS supplementation reduced (P < 0.05) NH₃ and H₂S emissions, along with a trend to reduce (P < 0.10) CH₄ generation in the initial stage in comparison to the CON diet. Furthermore, the faecal score in the experimental group was lower (P < 0.05) on day 42 compared to control animals. In conclusion, QS proved to be a suitable supplement for growing pigs as it improved growth efficiency and nutrient digestibility, as well as reduced gas emissions and faecal score.